Tracking the transport of europium-labeled polystyrene nanoplastics in natural soils: Insights from leaching tests under varied environmental condition

Nanoplastics pollution has become a significant environmental concern, particularly regarding its effects on soil ecosystems. This study investigates the vertical transport of europium-labeled polystyrene nanoplastics (Eu-NPs) in three distinct natural soils: high-calcium soil (HCS), red soil (RS), and black soil (BS). Leaching column experiments were conducted under simulated rainfall conditions to assess Eu-NP mobility, with concentrations quantified using inductively coupled plasma mass spectrometry (ICP-MS). Results revealed that Eu-NPs exhibited the greatest mobility in HCS, with vertical transport reaching 18 cm after three years of simulated rainfall. In contrast, RS and BS showed minimal transport, with maximum distances of 4 cm and 2 cm, respectively. Temperature fluctuations were found to influence Eu-NPs transport, particularly in HCS, where higher temperatures reduced migration, likely due to enhanced agglomeration. Alternating wet-dry cycles further increased Eu-NP mobility in HCS, while minimal effects were observed in RS and BS. These findings underscore the complex interplay between soil physicochemical properties and environmental factors in governing nanoplastics transport. The study provides important insights into the environmental fate of polystyrene nanoplastics (PS NPs) in natural soils and contributes to bridging the knowledge gap between controlled laboratory assessments and real-world environmental conditions.